Fluid contacting trays are the flow control means inside towers, reactors and other vessels that are commonly utilized for both petroleum and chemical processes, such as fractionation, absorption, distillation, separation, recovery, refinement, or purification. Gases, vapors, or liquids are thoroughly mixed in a controlled manner for mass transfer, heat transfer, and/or chemical reactions as required for the specific process service. Tray decks are flat, elongated panels that utilize special orifices and valves to regulate flow that takes place inside towers and other vessels. Typically, gases, vapors, or liquids are contacted in a controlled manner by utilizing tray decks on which a predetermined amount of flow is maintained. These tray decks have a plurality of orifice holes or openings along their surface, which extend through the tray deck from one surface to the opposing surface. Gases, vapors, or liquids that are present below the tray deck flow through these orifices, thus contacting the liquid which is maintained on the upper surface of the tray deck, where the mass transfer, heat transfer, and/or chemical reactions all occur.
The orifices in the tray deck are closed with moving valves that control the flow of gases, vapors, and/or liquids from beneath the tray deck to the upper surface of the tray deck, and prevent backflow of liquid from above to below the tray deck. These valves help to regulate the amount of gas, vapor, or liquid that flows through the orifices, thus controlling the reaction (similar to a pop it valve). Their operation is a function of the flow rate of the gases or vapors that are introduced into the environment below the tray deck. This flow rate affects the gas, vapor, or liquid pressure beneath the tray deck, thus affecting the pressure experienced by each valve independently moving within its orifice. In operation, these flow rates can be relatively high, causing the valves not only to lift upward while positioned in the tray deck orifices, but also to move laterally and/or to rotate within the orifices. The metal legs that hold the valve in place and prevent the valve from being pushed upward through the orifices often cut and enlarge the orifices with their repeated rotation. Such rotation is detrimental, because over time, the rotating valve will wear down the inner surface of each of the orifices, thus causing them to grow larger and larger, until finally allowing the valve to be pushed through leaving an uncontrolled opening in the tray deck. In some situations, the orifices are enlarged by up to 20-30% larger than their original size. With respect to circular tray deck orifices, for example, they can become worn down such that their inner diameters grow larger. When this occurs, the mixing contact efficiency and pressure drop control both needed for the reaction are compromised because the liquid on the upper surface of the tray deck can flow freely down between the inner surface of the orifice and the valve. At the same time, the gases, vapors, and liquids below the tray deck can flow freely upward in the same manner. Without close regulation of the amount gas, vapor, and liquid that come into intimate contact with each other, the efficiency and control of the process is reduced.
The conventional method of solving this problem is to simply replace the tray deck periodically after it has experienced a detrimental amount of wear and tear. Replacement moving valves will no longer reliably stay in these worn down oversized tray deck orifices, so complete tray deck panel replacement is currently the only viable solution. However, after a few more years of the same service conditions, the exact same problem is very likely to re-occur. This not only requires costly and specialized custom made equipment panels, but it also requires regular entry maintenance of the enclosed vessel, which requires plant unit outage time, lost unit production, and ultimately increased unit operating costs.
Accordingly, the new orifice device herein eliminates the wear issue, and can repair existing tray deck enlarged orifices to prevent complete tray deck panel replacement.